Multivesicular exocytosis in rat pancreatic beta cells

AIMS/HYPOTHESIS

To establish the occurrence, modulation and functional significance of compound exocytosis in insulin-secreting beta cells.

METHODS

Exocytosis was monitored in rat beta cells by electrophysiological, biochemical and optical methods. The functional assays were complemented by three-dimensional reconstruction of confocal imaging, transmission and block face scanning electron microscopy to obtain ultrastructural evidence of compound exocytosis.

RESULTS

Compound exocytosis contributed marginally (<5% of events) to exocytosis elicited by glucose/membrane depolarisation alone. However, in beta cells stimulated by a combination of glucose and the muscarinic agonist carbachol, 15-20% of the release events were due to multivesicular exocytosis, but the frequency of exocytosis was not affected. The optical measurements suggest that carbachol should stimulate insulin secretion by ∼40%, similar to the observed enhancement of glucose-induced insulin secretion. The effects of carbachol were mimicked by elevating [Ca(2+)](i) from 0.2 to 2 μmol/l Ca(2+). Two-photon sulforhodamine imaging revealed exocytotic events about fivefold larger than single vesicles and that these structures, once formed, could persist for tens of seconds. Cells exposed to carbachol for 30 s contained long (1-2 μm) serpentine-like membrane structures adjacent to the plasma membrane. Three-dimensional electron microscopy confirmed the existence of fused multigranular aggregates within the beta cell, the frequency of which increased about fourfold in response to stimulation with carbachol.

CONCLUSIONS/INTERPRETATION

Although contributing marginally to glucose-induced insulin secretion, compound exocytosis becomes quantitatively significant under conditions associated with global elevation of cytoplasmic calcium. These findings suggest that compound exocytosis is a major contributor to the augmentation of glucose-induced insulin secretion by muscarinic receptor activation.

Establishing a new electrical conduction pathway by anastomosis of the right auricle and right ventricle assisted by mesenchymal stem cells in a canine model

BACKGROUND

Electronic pacemakers are the primary treatment of complete atrioventricular (AV) block, but their use is associated with many complications. The aim of the present study was to create an alternative treatment for these patients.

MATERIALS AND METHODS

Mesenchymal stem cells (MSCs) isolated from the bone marrow of a 3-month-old dog were cultured in vitro. The MSCs were labeled with 4', 6-diamidino-2-phenylindole (DAPI) before transplantation. We anastomosed the right auricle and right ventricle in 24 dogs, and transplanted labelled MSCs into the anastomotic area of 8 dog hearts. Using immunostaining we assessed survival and differentiation of the implanted cells at 8 weeks posttransplantation. Electrocardiography confirmed the secondary electrical conduction pathway.

RESULTS

The ventricular current was captured by the electronic pacemaker in 21 dogs. Compared with the control group (surgery alone), pacemaker stimulus current was significantly less in the MSC group (surgery+MSCs).

CONCLUSIONS

Anastomosis of the right auricle and right ventricle assisted by MSCs may be a new treatment for patients with complete AV block in the future.

An intelligent multi-restart memetic algorithm for box constrained global optimisation

In this paper, we propose a multi-restart memetic algorithm framework for box constrained global continuous optimisation. In this framework, an evolutionary algorithm (EA) and a local optimizer are employed as separated building blocks. The EA is used to explore the search space for very promising solutions (e.g., solutions in the attraction basin of the global optimum) through its exploration capability and previous EA search history, and local search is used to improve these promising solutions to local optima. An estimation of distribution algorithm (EDA) combined with a derivative free local optimizer, called NEWUOA (M. Powell, Developments of NEWUOA for minimization without derivatives. Journal of Numerical Analysis, 28:649-664, 2008), is developed based on this framework and empirically compared with several well-known EAs on a set of 40 commonly used test functions. The main components of the specific algorithm include: (1) an adaptive multivariate probability model, (2) a multiple sampling strategy, (3) decoupling of the hybridisation strategy, and (4) a restart mechanism. The adaptive multivariate probability model and multiple sampling strategy are designed to enhance the exploration capability. The restart mechanism attempts to make the search escape from local optima, resorting to previous search history. Comparison results show that the algorithm is comparable with the best known EAs, including the winner of the 2005 IEEE Congress on Evolutionary Computation (CEC2005), and significantly better than the others in terms of both the solution quality and computational cost.

Novel brain targeting prodrugs of naproxen based on dimethylamino group with various linkages

As a preventive and treatment drug for Alzheimer's disease (AD), naproxen's clinical application is hampered by its limited distribution in the brain. To increase the delivery of naproxen across the blood-brain barrier (BBB), 3 prodrugs (P1, P2 and P3) of naproxen were synthesized through either ester bond or amido bond using the dimethylamino moiety as a brain-targeting ligand. The in vitro release of naproxen from the 3 prodrugs was studied in PBS, rat plasma and brain homogenate. P3 with an amido bond appeared to be highly stable in all incubation media, whereas P1 and P2 with ester bonds were partially hydrolyzed in alkaline environment and brain homogenate to yield the parent drug. After i. v. administration to rats, the brain concentration of total naproxen (summation of released and bound naproxen, TN) of P1, P2 and P3 groups were 28.81, 24.51 and 15.54 times greater than that of the control naproxen group at 5 min, respectively, and the brain AUC0-t were 6.94, 10.06 and 6.70 times greater than that of the control naproxen group. In addition, the Cmax of TN in the brain after the administration of prodrugs with ester bonds (P1 and P2) was higher than that of the amide prodrug (P3). The results highlighted the possibility of brain delivery of naproxen using prodrug strategies based on the brain-targeting ligand with dimethylamino moiety, in which the linkage between drug and targeting group might play an important role in modulating the in vivo behaviors of these prodrugs.

Integration of proteomics into systems biology of cancer

Deciphering the complexity and heterogeneity of cancer, benefits from integration of proteomic level data into systems biology efforts. The opportunities available as a result of advances in proteomic technologies, the successes to date, and the challenges involved in integrating diverse datasets are addressed in this review.

Ribosomal protein S14 unties the MDM2-p53 loop upon ribosomal stress

The MDM2-p53 feedback loop is crucially important for restricting p53 level and activity during normal cell growth and proliferation, and is thus subjected to dynamic regulation in order for cells to activate p53 upon various stress signals. Several ribosomal proteins, such as RPL11, RPL5, RPL23, RPL26 or RPS7, have been shown to have a role in regulation of this feedback loop in response to ribosomal stress. Here, we identify another ribosomal protein S14, which is highly associated with 5q-syndrome, as a novel activator of p53 by inhibiting MDM2 activity. We found that RPS14, but not RPS19, binds to the central acidic domain of MDM2, similar to RPL5 and RPL23, and inhibits its E3 ubiquitin ligase activity toward p53. This RPS14-MDM2 binding was induced upon ribosomal stress caused by actinomycin D or mycophenolic acid. Overexpression of RPS14, but not RPS19, elevated p53 level and activity, leading to G1 or G2 arrest. Conversely, knockdown of RPS14 alleviated p53 induction by these two reagents. Interestingly, knockdown of either RPS14 or RPS19 caused a ribosomal stress that led to p53 activation, which was impaired by further knocking down the level of RPL11 or RPL5. Together, our results demonstrate that RPS14 and RPS19 have distinct roles in regulating the MDM2-p53 feedback loop in response to ribosomal stress.

Enzymatic synthesis oF L-tryptophan from D,L-2-amino-delta2-thiazoline-4-carboxylic acid and indole by Pseudomonas sp. TS1138 L-2-amino-delta2-thiazoline-4-carboxylic acid hydrolase, S-carbamyl-L-cysteine amidohydrolase, and Escherichia coli L-tryptophanase

L-Tryptophan (L-Trp) is an essential amino acid. It is widely used in medical, health and food products, so a low-cost supply is needed. There are 4 methods for L-Trp production: chemical synthesis, extraction, enzymatic synthesis, and fermentation. In this study, we produced a recombinant bacterial strain pET-tnaA of Escherichia coli which has the L-tryptophanase gene. Using the pET-tnaA E. coli and the strain TS1138 of Pseudomonas sp., a one-pot enzymatic synthesis of L-Trp was developed. Pseudomonas sp. TS1138 was added to a solution of D,L-2-amino-delta2-thiazoline-4-carboxylic acid (DL-ATC) to convert it to L-cysteine (L-Cys). After concentration, E. coli BL21 (DE 3) cells including plasmid pET-tnaA, indole, and pyridoxal 5'-phosphate were added. At the optimum conditions, the conversion rates of DL-ATC and L-Cys were 95.4% and 92.1%, respectively. After purifying using macroporous resin S8 and NKA-II, 10.32 g of L-Trp of 98.3% purity was obtained. This study established methods for one-pot enzymatic synthesis and separation of L-Trp. This method of producing L-Trp is more environmentally sound than methods using chemical synthesis, and it lays the foundations for industrial production of L-Trp from DL-ATC and indole.

Predictors of remission with placebo using an integrated study database from patients with major depressive disorder

OBJECTIVE

To identify predictors of remission with placebo treatment in double-blind randomized controlled trials (RCTs) in major depressive disorder (MDD).

METHOD

A total of 1017 placebo-treated patients with baseline Hamilton Depression rating scale (HAMD) total ≥15 from eight duloxetine RCTs were included. Remission was defined as endpoint (7-8 weeks) HAMD total ≤7. Data were randomly split into training data (N = 813, 80%) for model selection and test data (N = 204, 20%) for validation. Logistic regression and classification and regression tree (CART) methods were used to identify predictors of remission. Predictive accuracy of models was assessed by Receiver Operator Characteristic (ROC) curves.

RESULTS

Baseline predictors for remission with placebo consistently identified with the logistic regression and CART analysis were less severe depressive symptoms (based on HAMD core symptoms), younger age, less anxiety (based on HAMD anxiety/somatization), and shorter current MDD episode duration. Associated cut-off values from the CART method characterized patient groups according to their remission likelihood. However, the predictive accuracy was modest for both methods with areas under the ROC curve of 0.6-0.65 based on test data.

CONCLUSION

The derived models, although of limited value for predicting remission in individual patients, may be useful for adjusting for placebo effects in clinical trials.

Hydrogen-rich saline alleviates experimental noise-induced hearing loss in guinea pigs

OBJECTIVE

To examine the efficiency of hydrogen-rich saline in the treatment of intensive noise-induced cochlear injury.

MATERIALS AND METHODS

Forty guinea pigs were assigned to one of four groups: HS+NOISE (i.p. injection hydrogen-rich saline), NS+NOISE (i.p. injection normal saline), NOISE ALONE (noise control), and NO TREATMENT (normal control) groups. The HS+NOISE, NS+NOISE, and NOISE ALONE groups were exposed to intensive noise (4 h at 115 dB SPL noise of 4000±100 Hz). The auditory brainstem response (ABR) was used to examine the hearing threshold in each group. Distortion product otoacoustic emission (DPOAE) was used to examine outer hair cell function. We also examined cochlear morphology to evaluate inner and outer hair cell trauma induced by noise exposure. Hydrogen-rich saline was administered twice daily for 6 days (2.5 ml/kg, i.p.) 24 h after noise exposure.

RESULTS

Baseline ABR thresholds and DPOAE values were normal in all groups at the measured frequencies (2, 4, 8, and 16 kHz) before noise exposure. The ABR threshold shift was 50-55 dB across the frequencies tested, and average DPOAE declined in the NOISE ALONE, NS+NOISE, and HS+NOISE groups 24 h after noise exposure. However, the changes in cochlear parameters were different between groups. The HS+NOISE group showed a significantly decreased ABR threshold value as compared with the NS+NOISE or NOISE ALONE group (P<0.01) on day 7. The mean DPOAE recovered to some extent in the three noise exposure groups, but at most frequencies the HS+NOISE group showed significantly increased DPOAE on day 7 as compared with the NS+NOISE group or NOISE ALONE group (P<0.01). Surface Corti organ preparations stained with succinate dehydrogenase (SDH) showed that most outer hair cells (OHCs) were still dropsical and a few were missing 7 days after noise exposure in the NS+NOISE group. Only a few OHCs were slightly dropsical in the HS+NOISE group. The numbers of missing hair cells 7 days after noise exposure were significantly greater in the NOISE ONLY and NS+NOISE groups than the HS+NOISE group (P<0.01).

CONCLUSIONS

Hydrogen-rich saline can alleviate experimental noise-induced hearing loss in guinea pigs, partially by preventing the death of cochlear hair cells after intensive noise exposure.

Common features in the microscopic dynamics of hydration water on organic and inorganic surfaces

The microscopic dynamics of hydration water exhibits some universal features that do not depend on the nature of the hydrated surface. We show that the hydration level dependence of the dynamic transition in the mean squared atomic displacements measured by means of elastic neutron scattering is qualitatively similar for hydration water in inorganic and organic hosts. The difference is that the former are 'rigid', whereas the dynamics of the latter can be enhanced by the motions of the hydration water. The overall hydration level appears to be the main parameter governing the magnitude of the mean squared atomic displacements in the hydration water, irrespective of the details of the hydrated host.

Cascaded frequency upconversion for high-speed single-photon detection at 1550 nm

We present a device for two-stage frequency upconversion of single-photon-level signals in the 1.55 μm telecom band to the green spectral region with low excess noise, suitable for detection by low-timing-jitter silicon single-photon avalanche photodiodes (APDs). We achieve a net conversion efficiency of 87% and a system timing jitter below 70 ps FWHM, dominated by the jitter of the APD. Modifications of our device are suitable for downconversion of single photons from visible-wavelength quantum emitters into the telecom band.

Time to treatment initiation with oral antihyperglycaemic therapy in US patients with newly diagnosed type 2 diabetes

AIM

To compare the time from initial diagnosis to initiation with oral antihyperglycaemic treatment in younger versus older patients with type 2 diabetes, and to evaluate factors associated with initiating treatment.

METHODS

This was a retrospective US cohort study with a 2-year follow-up period after diagnosis of type 2 diabetes. Using the General Electric Healthcare's Clinical Data Services electronic medical record database, eligible patients included those aged ≥30 years at initial diagnosis of type 2 diabetes between January 2003 and December 2005. In the 2-year period following diagnosis, the time to the first prescription of an oral antihyperglycaemic agent was compared between younger (30-64 years) and older (≥65 years) patients. Factors associated with time to treatment with an oral antihyperglycaemic agent were examined using Cox proportional hazards regression.

RESULTS

Of the 10 743 patients with newly diagnosed type 2 diabetes, 43% were ≥65 years old. The mean age at diagnosis was 73 years for older patients and 52 years for younger patients. Compared to younger patients, a greater proportion of older patients had a baseline haemoglobin A1c (HbA1c) value <7% (38 vs. 32%; p < 0.001). In the 2-year follow-up period, a significantly greater proportion of younger patients (59%) received oral antihyperglycaemic treatment compared to older patients (44%; p < 0.001). The median time between diagnosis and initiating treatment with an oral antihyperglycaemic agent was 350 days for younger patients and >2 years for older patients. After adjusting for covariates, older patients had a greater risk of not receiving treatment with oral antihyperglycaemic therapy than younger patients [adjusted hazard ratio = 0.82 (95% confidence interval: 0.75, 0.90)].

CONCLUSIONS

In patients with newly diagnosed type 2 diabetes, the time to initiation of oral antihyperglycaemic therapy was significantly longer in older patients (≥65 years old) than younger patients (<65 years).

Detection of Breast Lesions using an Automated Breast Volume Scanner System

OBJECTIVE: This study investigated the clinical utility of an automated breast volume scanner (ABVS) system for the detection of breast lesions. METHODS: The breasts of 81 patients referred for ultrasonographic examination were scanned using the ABVS system and handheld ultrasonography independently by two experienced examiners. The ABVS was used to perform scans of the breast in three directions (anteroposterior, lateral and medial), with the addition of further inferior and superior scans if necessary. The scanning data were then stored and automatically reconstructed. For hand-held ultrasonography the whole breast was scanned radially from the outside to the centre of the nipple. RESULTS: The numbers of lesions reported by the two examiners were 89 and 99, respectively, using the ABVS (not statistically significant), compared with 60 and 85, respectively, using handheld ultrasonography (statistically significant). CONCLUSIONS: The ABVS system is an operator-independent method for automated breast scanning. It detected more breast lesions and provided additional information for the diagnosis of intraductal and malignant lesions compared with hand-held ultrasonography.

Characterizing ultrafine particles and other air pollutants at five schools in South Texas

This study examined five schools with different ventilation systems in both urban and rural areas in South Texas. Total particle number concentration, ultrafine particle (UFP, diameter < 100 nm) size distribution, PM(2.5) , and CO(2) were measured simultaneously inside and outside of various school microenvironments. Human activities, ventilation settings, and occupancy were recorded. The study found a greater variation of indoor particle number concentration (0.6 × 10(3) -29.3 × 10(3) #/cm(3) ) than of outdoor (1.6 × 10(3) -16.0 × 10(3) #/cm(3) ). The most important factors affecting indoor UFP levels were related to various indoor sources. Gas fan heaters increased the indoor-to-outdoor ratio (I/O ratio) of total particle number concentrations to 30.0. Food-related activities, cleaning, and painting also contributed to the increased indoor particle number concentration with I/O ratios larger than 1.0. Without indoor sources, the I/O ratios for total particles varied from 0.12 to 0.66 for the five ventilation systems studied. The I/O ratio decreased when the outdoor total particle number concentration increased. Particles with diameters <60 nm were less likely to penetrate and stay airborne in indoor environments than larger particles and were measured with smaller I/O ratios.

PRACTICAL IMPLICATIONS

From an exposure assessment perspective, schools are important and little-studied microenvironments where students congregate and spend a large proportion of their active time. This study provides information for indoor and outdoor ultrafine particle concentrations at different types of school microenvironments. These data may allow future epidemiological studies to better estimate exposure and assess ultrafine particles health effects among students.